Rotors can be used in a variety of applications, including, for example, a brake system for a vehicle or a single or multiple friction disc for use in a clutching system for a transmission.
A brake system can use a brake rotor that can be mounted to a wheel hub and rotates with the wheel as the automobile moves. A brake pad is located on each side of the brake rotor in a plane parallel to the plane of the brake rotor. The brake pads are in a fixed position with respect to the brake rotor and wheel. To actuate the braking system, a hydraulic fluid is forced into a piston which presses the brake pads against the rotating brake rotor thereby slowing the wheel hub and wheel.
Similarly, a transmission can use a clutch pack assembly having one or more pressure rotors, similar to a brake rotor, and one or more friction discs, similar in function to brake pads. When the transmission is in “neutral,” the pressure rotors are separated in space from the parallel friction discs. When the transmission is engaged, the pressure rotors contact the adjacent friction discs.
However, prior art metal rotors can be subject to significant and destructive amounts of friction during operation. In a demanding or extreme environment, for example, the friction created by the force of brake pads pressing against a brake rotor can generate enough heat to damage metal brake rotors. Heating of the brake rotor leads to expansion of the metal brake rotor. Excessive heat can lead to expansion of the metal rotor resulting in brake rotor deformation, also known as warping. Warping of the brake rotor can lead to drastically decreased brake performance because the contact area of brake pads to the brake rotor is decreased. Furthermore, the brake pedal of the braking system can pulsate or vibrate due to “kick-back” of the brake piston resulting from a warped metal rotor.
Expansion as a result of excessive heat build up in a metal pressure rotor used in a clutching system can also cause deformation and warping that result in a reduction of a pre-engineered clearance between the pressure rotor and the adjacent friction disc. As the pressure rotor deforms, the contact area between the pressure rotor and the friction disc is reduced in size to just the “high spots” on the pressure rotor. A secondary failure caused by deformation can occur when contact is made between the pressure rotor and the friction disc when the clutch is adapted to be in neutral, thereby engaging the output of the transmission when no output is desired.
Prior art braking systems have attempted to mitigate or prevent heat damage to brake rotors. Ceramic coated brake rotors can be effective at resisting heat absorption and will not warp at temperatures that would otherwise cause a metal brake rotor to deform. However, a limitation of prior art ceramic coated brake rotors is that they are expensive to produce. Metal brake rotors can be “vented” by providing, for example, a corrugated layer between the first and second sides of the brake rotor in order to provide air cooling. A limitation of prior art vented rotors is that they are larger and heavier, thereby requiring a heavier duty braking system and increasing the unsprung weight of the automobile which decreases the automobile's handling, acceleration, deceleration, and fuel efficiency. Metal brake rotors can be “cross-drilled” by drilling one or more holes in the plane of the brake rotor to allow a larger surface area for heat dissipation and for air flow through and around the brake rotor. A limitation of prior art cross-drilled rotors is that the contact area for the brake-pad-to-brake-rotor interface is decreased, thus decreasing the braking performance of the brake system.
Similarly, a rotor in a clutch pack for a transmission is subject to the same frictional forces and heat damage as is a brake rotor. Prior art rotors for transmissions are heavier to prevent warping that would adversely impact the performance of friction rotor.
Accordingly, there is a need for a rotor that is light, inexpensive, and resists warping and that can increase the efficiency of prior art systems.